The end credits note that "Patrick Wymark appears by permission of the Governors of the Royal Shakespeare Company".
Wilder was with Wesley Todd in Germany in 1945, when the latter was tracking Nazi war criminals.
At 35:32 an insect lands and crawls around the picture. This wouldn't have been present on original transmission - it's been captured during the telerecording process, where a film camera would be pointed at a special monitor and record its output - including any errant bugs which may stray across the screen.